1. Field of the Invention
The present invention relates to a punching processing apparatus, a sheet post-processing apparatus, and an image forming apparatus.
2. Description of the Related Art
In image forming apparatuses such as copiers, printers, facsimiles, and printing machines, image outputs can be obtained by forming visible images such as toner images on sheets. Unlike a case where the sheets are sequentially discharged to discharge trays from the image forming apparatuses, sheets after image forming are in some cases conveyed to sheet post-processing apparatuses that perform post-processing, such as punching the sheets for filing, affixing seals, or adding information on the sheets, and the sheets are sorted into sheet groups.
The sheet post-processing apparatuses are mostly used by being connected at the sheet discharge positions of the image forming apparatuses. In an example of the such sheet post-processing apparatuses, a sheet conveyed into the sheet post-processing apparatus is subjected to punching processing for filing and then to succeeding processing such as binding processing, and thereafter discharged. One of the reasons why the punching processing is performed first is that, when the binding processing is performed as the next processing, it is difficult to perform punching because staples used in the binding processing hinder the punching.
In punching, punched holes are formed in a predetermined edge area of the conveyed sheet. There are various types of punched holes. For a typical example, two holes, three holes, and four holes are frequently used in Japan and in Europe. As for a diameter of a punched hole in punching, two holes having a diameter of 6.5 mm are used in Japan whereas two holes or three holes having a diameter of 8 mm are selected in some cases in North America, and in Europe, four holes having a diameter of 6.5 mm are used. In Northern Europe, four holes arranged with uneven intervals are selected in some cases. In addition to the types described above, multiple holes for a binder are used, for example.
Punching scraps produced in punching are collected by being dropped into a container such as a punching scrap collection member disposed at the punching processing position. The collected punching scraps are dropped and accumulated in the container. In most cases, as illustrated in FIG. 17, the collected punching scraps are accumulated like a mountain (indicated with the heavy two-dot chain line in FIG. 17). In recent years, with the downsizing of the apparatus, the size of the container tends to be reduced in volume. As a result, a frequency of disposal may be increased depending on an amount of the dropped and accumulated punching scraps.
A structure that detects the height of the accumulated punching scraps is well known as a structure for detecting disposal of the punching scraps. In the structure, a detection sensor provided at a predetermined height detects a full state of the punching scraps and warns of disposal of the punching scraps in the container.
In the case of the punching scraps accumulated like a mountain, the punching scraps may be accumulated in one part of the container. The whole of the container may not always be filled with the punching scrapes. Conventionally, a structure has been proposed in which a false detection due to the accumulation like a mountain is prevented and the punching scraps are efficiently collected by breaking down the punching scraps accumulated like a mountain. For example, refer to Japanese Patent No. 4592403 and Japanese Patent Application Laid-open No. 11-139674.
In Japanese Patent No. 4592403, punching processing apparatuses having the following structures are described. In the punching processing apparatus, a punching scrap housing unit is provided that can reciprocate in the horizontal direction in a punching scrap collection member, and punching scrapes are flattened out by reciprocating the punching scrap housing unit using excitation of a solenoid. In addition, in the other punching processing apparatus, the bottom surface of the punching scrap housing unit is an elastic body and the punching scraps are broken down and flattened out by vibrating the bottom portion. In Japanese Patent Application Laid-open No. 11-139674, a punching processing apparatus is described that has a structure in which punching scraps accumulated like a mountain are flattened out by knocking the bottom surface of a punching scrap collection member (punching scrap housing unit) so as to vibrate the punching scrap collection member. The reciprocating and vibrating are performed when a sensor is on that is provided to the punching scrap collection member or the punching scrap housing unit and detects the height of the punching scraps.
The structure described in Japanese Patent No. 4592403 requires a driving source for reciprocating or vibrating up and down the punching scrap housing unit to be provided in the vicinity of the punching scrap housing unit. The volume of the punching scrap housing unit provided in the punching scrap collection member is reduced due to the space for the driving source. As a result, it is difficult to reduce the frequency of disposal because the collection amount of punching scraps cannot be increased. The special driving source required for reciprocating or vibrating operation may increase the apparatus in size and increase cost due to an increase in the number of parts.
In the structure described in Japanese Patent Application Laid-open No. 11-139674, the vibrated punching scraps behave unstable because the punching scraps are flattened out by being vibrated. For example, the punching scraps scatter as far as the location of the sensor detecting the height. This may lead to a determination that the height of the accumulated punching scraps corresponds to the full state though the punching scraps is being vibrated and flattened out, and lower the detection accuracy.
Therefore, it is desirable to provide a punching processing apparatus that can be provided without an increase in size and cost, and avoid false detection of the height of the accumulated punching scraps, i.e., a false determination that the container is in a full state even though the state has been corrected to the actual state.